Device for detecting the absence of a finger in a type carrier of a printer

ABSTRACT

A device is provided for detecting the absence of a finger in a printer, comprising a mobile support provided with print-type support-fingers and with an equal number of synchronization marks, and a fixed detector of synchronization marks which sends a so-called synchronization pulse to a strike triggering member, whenever a mark is passing before it. The device is characterized in that it comprises a second fixed detector placed at the lever of the finger associated with the mark, which, during the displacement, passes before the first detector and delivers a pulse indicating the presence of a finger each time a finger is passing before it, and a two input recognition circuit, each input receiving respectively pulses delivered by the first and the second detector.

tinite States ,atent 91 [111 3,351,323 Fltgen Nov. 26, 1974 [54] DEVICE FOR DETECTING THE ABSENCE 3,656,426 4/1972 Potter 173 23 A OF A FINGER IN A TYPE CARRIER OF A PRINTER Inventor: Jean-Jacques Pierre Eltgen,

Danjoutin, France Assignee: Societe Honeywell Bull (Societe Anonyme), Paris, France Filed: May 22, 1973 Appl. No.2 362,726

Foreign Application Priority Data May 25, 1972 France 72.18665 US. Cl 340/267 R, 178/23 A, 340/259 Int. Cl. G08b 21/00 Field of Search 340/259, 267 R, 282;

References Cited UNITED STATES PATENTS 2/1968 Buss 340/259 Primary ExaminerDavid L. Trafton Attorney, Agent, or FirmFred Jacob [5 7 ABSTRACT A device is provided for detecting the absence of a finger in a printer, comprising a mobile support provided with print-type support-fingers and with an equal number of synchronization marks, and a fixed detector of synchronization marks which sends a socalled synchronization pulse to a strike triggering member, whenever a mark is passing before it. The device is characterized in that it comprises a second fixed detector placed at the lever of the finger associated with the mark, which, during the displacement, passes before the first detector and delivers a pulse indicating the presence of a finger each time a finger is passing before it, and a two input recognition circuit,

each input receiving respectively pulses delivered by v the first and the second detector.

6 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION The present invention concerns a device for the detection of the absence of a finger, intended particularly for a type support for a printer having print-type carrier -fingers.

Various print-type-support endless belts for a printer are well known. Such a belt is, for example, described in the French Pat. No. 1,602,392. This belt is metallic, made of steel, and mounted stretched over two pulleys of parallel rotating axes. It is equipped on its upper rim with N type-carrying fingers in the form of elastic tongues which correspond to an integer number of identical sets of different characters.

In the printer, these type-support fingers pass horizontally in a uniform linear movement before the writing medium and a striking assembly including striking motors each of which is capable of sequentially applying strike pulses to the characters by means ofa striking hammer. On its lower rim, this belt possesses N aligned synchronization holes, such that each of these holes is associated with a single one of the N characters. On a level different from the row of the N holes, is another synchronization hole called the initial belt hole which corresponds with a certain character among the N characters, this character being, for example, the first of a series of characters of one of the aforementioned sets. A first pickup (magnetic or opticelectronic) is associated with the group of N aligned holes and connected to the frame of the printer. This pickup emits a signal each time that a hole and consequently a character passes before it. This signal is amplified, given the proper form and sent to the logic of the printer.

ln the same manner, a second pickup linked to the frame of the printer is associated with the initial belt hole. It emits a signal each time that the latter passes before it. This signal, amplified and given proper form, is also sent to the logic of the printer.

Thus, it is easy to see that the combination of the signal emitted by the second pickup and of the assembly of N signals transmitted by the first pickup permits the exact tracing of each character, i.e., that one always knows which of the type-supporting fingers it is that passes before a particular hammer, or more exactly, the synchronization hole corresponding with that typesupporting finger, but one does not know if that finger is physically present. In other words, the probability that the finger is absent, either due to destruction or deformation, is not nil, as will be explained hereinafter.

Printers with type-support belts exhibit the following characteristic. When a character receives the impact of a print hammer, the character-carrying finger deforms to enable the character -to remain facing the corresponding printing position as long as the impact of said hammer lasts.

Obviously, when one wishes to have printers capable of acclelerated performances by increasing the passing speed, the tongues are subjected to considerable stresses which may entail certain number of consequences which could interfere with the normal functioning of the printer. Deformation of the finger by torsion, for instance, could cause serious damages to other parts of the machine, such as the ink ribbon, for example. Breaking of a finger which entails a loss of real information in each instant in which a print hammer strikes the writing medium, in the place of this absent finger, is not acceptable in view of the strict requirements actually imposed on printers, as far as the completeness of data is concerned.

It is, therefore, necessary, to add to the synchronization device a recognition circuit and an alerting circuit which enable it, on the one hand, to detect rapidly either the absence or the deterioration ofa finger, and on the other hand, to alert the printer to interrupt its operation.

SUMMARY OF THE INVENTION The present invention provides a remedy for the mentioned drawbacks, by verifying that for each synchronization hole the corresponding finger is indeed present.

The object of the invention is a device for the detection of the absence of a finger for the character support, of printers with type-carrying fingers.

The invention applies to printers comprising, on the one hand, a movable support equipped with print-type carrying fingers and synchronization marks in equal number, each mark being associated with a finger, and on the other hand, a fixed detector for the synchronization marks, placed close to the path followed by said marks, this detector sending a pulse of so-called synchronization to a strike-triggering member whenever a mark is passing before it, and the invention concerns a device for the detection of the absence of fingers, characterized in that it comprises a second fixed detector close to the path followed by the fingers and positioned on the level of the finger associated with the mark which during the movement passes before the first detector, this second detector emitting a pulse signailing the presence of a finger, whenever afinger passes in front of it, and a recognition circuit with two inputs, each of which receive the pulses emitted by the first and by the second detector, respectively. This circuit verifies the correspondence between the pulses emitted by the two detectors and generates in its output a signal indicating the absence of a finger, if such correspondence is not established.

In another special mode of embodiment of the invention, the recognition circuit comprises a first and a second monostable circuit in series, a front-recognition circuit, a flip-flop circuit and a comparison circuit. The first monostable circuit receives the synchronization pulse and emits, in response thereto, a first pulse, sent, on the one hand, to the second monostable circuit and, on the other hand, to the front-recognition circuit,

'while the second monostable emits, in response to that first pulse, a pulse called a window pulse, which is transmitted to the first input of the comparison circuit. The recognition circuit emits, in response to that first pulse, a signal sent to the first input of said flip-flop circuit whose second input receives the pulse, signalling the presence of a finger, the signal transmitted to the first input placing the flip-flop into its first state of equilibrium, and the pulse indicating the presence of a finger, placing it into the second state of equilibrium. The output signal received in the output of the said flip-flop circuit being sent to the second input of the comparison circuit which verifies if the same flip-flop circuit is not in its first state of equilibrium beyond the time interval defined by said window. The first detector is preferably formed by the association comprised of a magnetic pickup of variable reluctance whose output signal is amplified and put in proper form by an amplifier circuit.

In one type of special design of the invention, the second detector is identical with the first.

In another mode of embodiment of the invention, the second detector consists of the associated of an opticelectronic pickup comprising a light emitter and a photosensitive detector, also a circuit for amplification and proper forming of the output signal of said opticelectronic pickup.

The invention applies more particularly to endless print-type carrying belts which are mounted stretched over two pulleys of parallel rotating axes.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood during the following description, presented with reference to the attached drawing, offering, for non-limitating explanatory purposes, a type of embodiment according to the invention. In these drawings:

FIG. la is a perspective view of the type-carrying belt with its synchronization holes and the corresponding pickups;

FIGS. 1b land 2 are enlarged partial views of FIG. la;

FIG. 3 presents the general principle of the embodiment of the detection according to the invention;

FIG. 4 exhibits a type of design of the detection device whose general principle is represented by FIG. 3; and

FIG. 5 is a chronomgram of signals taken at different points of the detection device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the example of design, described here, the device for the detection of a defective finger is designed to track down any possible defectiveness of any one of the type-carrying fingers of the endless belt 1 for a printer, as shown in perspective view in FIG. la. This endless belt, made of a metallic material, is represented as mounted in the printing machine over two pulleys 2 and 3 whose rotational axes Y, Y, and Y Y' are vertical. To facilitate the understanding of FIG. 1, only one portion 4 ofthe belt I has been illustrated with its typecarrying fingers 5 to 8.

These fingers have the shape of elastic tongues and are shown intentionally oversized in relation to the belt 1, so as to make FIG. la more distinct. The belt includes in all, N character-supporting fingers which correspond with an integer number of identical sets of different characters. In the example of the embodiment described here, N 480 which corresponds with sets of 48 characters or 8 sets of 60 characters each. Facing the fingers 5 to 8 four striking hammers 9 to 12 are represented, denoted by arrows. Four synchronization holes 13 to 16 are associated with the fingers 5 to 8, respectively. Only a single synchronization hole is associated with each finger. It should also be noted that the synchronization holes are aligned.

As shown in FIG. 1b, which is an enlarged view of the portion 4 of the belt 1, the synchronization holes are positioned between the type-carrying fingers; thus the hole 14 is located between the fingers 5 and 6, the hole 15 between the fingers 6 and 7 etc. When the belt I passes in the direction of the arrow F, as indicated in FIGS. 1a land 1b, the hole 13 is associated with the finger 5, the hole 14 with the finger 6, the hole 15 with the finger 7, and so forth.

The type-carrying belt 1 furthermore comprises a special synchronization hole 17, called an initial belt hole. This hole is located at a level different from the alignment of the synchronization holes. To bring out this fact more clearly, four supplementary synchronization holes 18 to 21 have been represented below the initial belt hole 17.

With the row of N synchronization holes there is associated a pickup C,, called synchronization," connected to the frame of the printer and positioned in the immediate vicinity of the path followed by the N holes. This pickup is symbolized in FIG. 1 by an arrow. This may be a magnetic pickup with variable reluctance or an optic-electronic pickup. It emits a pulse whenever one of the synchronization holes passes before it. This pulse, amplified and put in proper form, is transmitted to the logic of the printer.

In the same manner, a pickup C identical with C,, symbolized by an arrow in the FIG. la, is associated with the initial belt hole 17. This pickup C emits a pulse which, after amplification, is sent to the logic of the printer. It should be noted that these arrows denote the directions in which the pickups operate. The latter may be located on both sides of the charactersupporting belt 1.

The combination of the signal sent by the second pickup C and of the signals emitted by the first pickup C,, permits in a known manner the tracing by said logic of every one of the synchronization holes, and consequently, of every one of the N fingers, provided however, that none of these has been subjected to a deterioration (breaking, deformation). In fact, the previously described assembly, i.e., the N synchronization holes, the initial belt hole 17, the pickups C, and C and their corresponding amplifiers, does not provide the knowledge as to whether the N fingers are indeed present. In other words, if a finger is broken or deteriorated, the printer strike logic does not know it and may continue to give orders to strike it.

It is the purpose of the invention to verify that for each synchronization hole the corresponding typecarrying finger is actually present, and if so is not the case, to signal the printer logic and to trigger a warning signal. For this purpose, a third pickup C as shown in FIG. 2, is provided, called a finger pickup," which is identical with C, and C on the level of the typesupporting fingers. This pickup is linked with the frame of the printer and placed in the immediate vicinity of the path followed by these fingers. The pickup C is positioned above the pickup C, (see FIG. 2) on the same vertical line. The part (4) OF the type-carrying belt 1 is represented in FIG. 2 with its fingers 5 to 8 and the corresponding synchronization holes 13 to 16. The synchronization pickup C, is also illustrated.

A circuit 30 for the detection of a finger, whose design principle is shown in FIG. 3, is associated with the pickups C, and C This circuit 30 includes the amplifiers 31 and 32 associated with the pickups C, and C, respectively, the recognition device 33 and the alarm device 34.

The synchronization pickup C, delivers, at the passage ofeach synchronization hole, a signal which is amplified, and put in proper form by the amplifier 31. The

latter transmits a pulse CS to one of the two inputs of the recognition circuit 33.

The finger pickup C emits, at the passage of each finger, a signal which is applied and put into proper form by the amplifier 32, which emits a pulse CD that is transmitted to the second input of the recognition circuit 33.

The recognition circuit 33 ascertains that for every pulse CS, corresponding with a determined synchronization hole, there does exist a with the finger associated with that hole.

The recognition circuit 33 is shown in greater detail in FIG. 4. It includes a first monostable circuit 35, a second monostable circuit 36, a recognition circuit of ascending front 37, a flip-flop 38, and a comparison circuit 39. The amplifiers 31 and 32 are also represented in the same illustration.

The operation of the recognition circuit 33 is illustrated in FIG. 5 by the chronogram of signals taken at the output of different parts making up the recognition circuit 33 and of the amplifiers 31 and 32. In FIG. 5, 1,, was taken as initial time, the instant in which a certain synchronization hole, for example, the hole 13, (see FIG. 2) passes in front of the synchronization pickup C,.

Three'cases of operation will be investigated successively:

I. The case in which the finger 9 is, for example, normal;

2. The case in which the finger 10, for example, is deteriorated, the finger being called beyond tolerance; and

3. The casein which the finger II, for example, is absent.

These three cases are compiled in the chronogram of FIG. 5 and illustrated from the instants 1 1' and 1",,, respectively. It is quite obvious that these cases are assembled arbitrarily to facilitate an understanding of the operation of the circuit 33, but in reality the probability that three cases will occur in three successive fingers is almost nil.

At the passage of the hole 13 before the synchronization pickup C,, the amplifier 31 emits a pulse CS equal to logic I between the instants 1,, and 1,. This pulse CS is transmitted to the input of the first monostable 35 and triggers the latter at the instant t The monostable 35 whose output signal M, before the instant 1,, was equal to logic 1 drops to zero logic at the instant 1, and rises again to logic I at the instant 1 with 1 1,. The signal M, is sent, on the one hand, to the input of the secpulse CD corresponding 0nd monostable 36 and, on the other hand, to the input of the recognition circuit of the ascending front 27. At the instant t in which the signal M, rises again, the monostable 36 is locked. This monostable 36 whose output signal F, before the instant 1 was equal to logic I, then drops to logic zero at the instant t to ascend again, thereafter, to logic I at the instant 1, with 1, 1 T;. The part of the signal during which the signal F is equal to logic zero is called the window F,.

Irrespective of which the three above considered cases occurs, the signals CS, M,, F take place at the time, identically to themselves, at the passage of each synchronization hole. This results clearly from FIGS. 5a to 50, where the signals CS occur, identically with themselves, between the instants 1,, and 1,, 1' and 1',, 1" and 1",, etc.

The signals M, between the instants 1,, and 1 1' 1",, and 1" etc. the signals F, between the instants 1 and t 1' and t.,, 1" and 1", (windows F1, F2, F3).

The monostables 35 and 36 are so arranged that the instants 1 1' 1",,, centers of the successive windows F,, F F are such as:

is located in the interior of the window signal F, centered in the middle of two pulses CS corresponding with two synchronization holes surrounding this finger.

The second monostable 36 permits the adjustment of the width T of the windows F,, F F etc. to a correct value by keeping in mind the accepted tolerances for the positions of the fingers. If the first case (finger 9 present) is considered, the pulse CD is located in the interior of the window F,. This pulse is a negative one which drops to logic zero at the instant 1 to rise again to logic I at the instant 1,, with 1, 1 1, and 1, 1,, 1, (see FIG. 5e). At the moment at which the window F, is generated (instant I the recognition circuit of the ascending front 37 causes the flip-flop 38 (state I) to rise. In the output Q of that flip-flop, the signal B is received which is sent to the second input ofthe comparison circuit 39. This signal B which rises to logic I at the :instant 1 drops again to logic zero at the instant 1 in which the pulse CD appears (flip-flop 38) at the zero state. It may be seen then, that when a finger is present, the output of the flip-flop is reduced to' zero before the closing of the window F, (instant 1,).

From this it follows that to verify whether a finger is present it suffices that the flip-flop 38 not be in the state 1 (signal B equal to logic 1 outside the window F corresponding with that finger (windows F,, F F etc. This verification is performed by the comparison circuit 39. The latter is a simple AND gate which,

in the case of the present design, consists of the association in series of a NOT-AND circuit 40 (more commonly called NAND according to the Anglo-Saxon terminology) and an inverter 41.

Now the second case is considered (finger l0 beyond tolerance). The pulse CD appears at the instant 1' 1,. The signal B is equal to logic 1 up to that moment 1' As between the instants 1, and 1' the signal F is equal 7 to logic I in the output of the AND circuit 39 a signal ALARM F.B equal to logic I (see FIG. 5f) is received between these instants.

Finally, the third case (finger ll absent) will be considered. The signal CD does not appear, the flip-flop 38 remains in the state I, and the signal B remains equal to logic 1 until a new pulse CD appears corresponding to the passage of the present following finger. Since,

however, from the instant l" the signal F rises again to logic 1, it follows that the signal ALARM P8 remains equal to logic 1 until a new finger appears. This ALARM signal triggers the altering device 34 in the second and in the third case.

Besides the gain of additional operational reliability, the device for the detection of a defective finger may be utilized for enhancing the readiness of the printing machine. For, when an ALARM signal appears, and if the logic of the printer is so conceived as to store the number of the defective finger (this is easy since the printing is controlled by a counter reduced to zero at the start of the belt by the signal of the pickup C and increased by l at each passage of a synchronization hole) the printing may be continued in a reduced manner due to a logical inhibiting of the defective finger by preventing the continued striking of this finger by the hammers.

This supplementary task given to the device for detection of a defective finger makes it possible to continue the work, through with slightly inferior results, while awaiting the delivery of a new belt and, in this way, one would even avoid the costly tying up any printing machine for a replacement belt.

It is apparent that the invention is by no means limited to a print-type carrying endless belt. It may equally well be applied to a printer, called daisy printer, in which the type-carrying fingers are arranged in the form of a fan, like the petals of a daisy.

What is claimed is:

l. A device for the detection of the displacement of a finger for a printer comprising a movable support in the form of an endless band carrying print-typecarrying fingers subject to deformation relative thereto and synchronization marks in equal number, each mark being associated with one finger, and a first fixed detector for the synchronization marks positioned close to the path followed by said synchronization marks; said first detector having means for sending a synchronization pulse whenever a synchronization mark passes before it; a second fixed detector positioned close to the path followed by the fingers and on the level of the finger associated with the mark that passes before the first detector, said second detector having means for emitting a pulse indicative of the presence of a finger whenever a finger passes before it, and a recognition circuit having two inputs for receiving the pulses emitted by the first and the second detector, respectively, said circuit having an output and means for verifying the correspondence between the pulses emitted by the two detectors and generating at said output a signal indicating the displacement of a finger whenever the correspondence is not established.

2. A device according to claim 1 in which the recognition circuit verifying means includes a first and a second monostable circuit in series, a front-recognition circuit, a flip-flop circuit having first and second inputs and an output Q and a comparison circuit having first and second inputs, the first monostable circuit having means for receiving the synchronization pulse and sending in response thereto a first pulse to the second monostable circuit and to the front-recognition circuit, the second monostable having means for delivering in response to the first pulse a window pulse to the first input of the comparison circuit, the front-recognition circuit having means for sending in response to that same first pulse a signal to the first input of said flipflop circuit, means for delivering to the second input of said flip-flop circuit the pulse indicative of the presence of the finger, the flip-flop circuit being of a construction wherein the signal transmitted to the flip-flop circuit first input puts the flip-flop circuit in a first state of equilibrium and the pulse indicative of the presence of a finger puts the flip-flop circuit in the second state of equilibrium, means for transmitting the output signal received in the output 0 of the flip-flop circuit to the second input of the comparison circuit; and said comparison circuit having means for verifying if said flipflop circuit is not in its first state of equilibrium beyond the time interval defined by said window pulse.

3. A device according to claim 1 in which the first detector includes a magnetic pickup of variable reluctance and a circuit for the amplification and forming of signals.

4. A device according to claim 1, in which the second detector includes a magnetic pickup of variable reluctance and a circuit for the amplification and forming of signals.

5. A device according to claim 1, in which the second detector includes the optic-electric pick-up including a light emitter and a photosensitive detector and a circuit for the amplification and forming of signals.

6. A device according to claim 1, in which two pulleys of parallel rotational axes support the endless band. 

1. A device for the detection of the displacement of a finger for a printer comprising a movable support in the form of an endless band carrying print-type-carrying fingers subject to deformation relative thereto and synchronization marks in equal number, each mark being associated with one finger, and a first fixed detector for the synchronization marks positioned close to the path followed by said synchronization marks; said first detector having means for sending a synchronization pulse whenever a synchronization mark passes before it; a second fixed detector positioned close to the path followed by the fingers and on the level of the finger associated with the mark that passes before the first detector, said second detector having means for emitting a pulse indicative of the presence of a finger whenever a finger passes before it, and a recognition circuit having two inputs for receiving the pulses emitted by the first and the second detector, respectively, said circuit having an output and means for verifying the correspondence between the pulses emitted by the two detectors and generating at said output a signal indicating the displacement of a finger whenever the correspondence is not established.
 2. A device according to claim 1 in which the recognition circuit verifying means includes a first and a second monostable circuit in series, a front-recognition circuit, a flip-flop circuit having first and second inputs and an output Q and a comparison circuit having first and second inputs, the first monostable circuit having means for receiving the synchronization pulse and sending in response thereto a first pulse to the second monostable circuit and to the front-recognition circuit, the second monostable having means for delivering in response to the first pulse a window pulse to the first input of the comparison circuit, the front-recognition circuit having means for sending in response to that same first pulse a signal to the first input of said flip-flop circuit, means for delivering to the second input of said flip-flop circuit the pulse indicative of the presence of the finger, the flip-flop circuit being of a construction wherein the signal transmitted to the flip-flop circuit first input puts the flip-flop circuit in a first state of equilibrium and the pulse indicative of the presence of a finger puts the flip-flop circuit in the second state of equilibrium, means for transmitting the output signal received in the output Q of the flip-flop circuit to the second input of the comparison circuit; and said comparison circuit having means for verifying if said flip-flop circuit is not in its first state of equilibrium beyond the time interval defined by said window pulse.
 3. A device according to claim 1 in which the first detector includes a magnetic pickup of variable reluctance and a circuit for the amplification and forming of signals.
 4. A device according to claim 1, in which the second detector includes a magnetic pickup of variable reluctance and a circuit for the amplification and forming of signals.
 5. A device according to claim 1, in which the second detector includes the optic-electric pick-up including a light emitter and a photosensitive detector and a circuit for the amplification and forming of signals.
 6. A device according to claim 1, in which two pulleys of parallel rotational axes support the endless band. 